Mar 13, 2012
Core-shell nanoparticles further improve cycling stability of lithium-ion batteries
Among the various energy-storage systems that have been proposed, lithium-ion batteries (LIBs) are well positioned and designs are progressing continuously. In particular, a great deal of work has been devoted to exploiting novel anode materials in an effort to enhance the energy density of commercialized systems. Transition metal oxides (including binary and ternary phases with normal or inverse spinel structure) have attracted considerable attention due to their high theoretical capacities, which exceed 800 mAh/g.
Researchers have shown that the use of nano-sized materials in combination with an “electronic wiring layer” can improve battery performance by delivering long-term cycle life and high rate capability. Various morphological features of nano-sized transition metal oxides involving nanoparticles, nanorods, nanowires and nanotubes have been fabricated via a wide spectrum of synthetic methods, such as sol-gel, hydrothermal, coprecipitation, polymerized complex, electrospinning and colloidal crystal template processes.
In recent work, scientists at Ajou University, Korea, have successfully demonstrated the formation of monodispersed core/shell ferrite/C nanoparticles by a simple two-step solution chemical route: low-temperature thermolysis of metal oleates and pyrolysis of a carbon source for application as high-capacity LIB electrodes. These prepared Fe3O4/C and CoFe2O4/C nanoparticles consist of both a high-capacity active core (ferrites) and an electroconductive shell (thin amorphous carbon) to bypass the drawbacks suffered through the facile aggregation of lithium-active nanoparticle electrodes.
Enhanced electron transport
The CoFe2O4/C nanocomposite electrodes show a high specific capacity that can exceed 700 mAh/g even after 200 cycles, along with enhanced cycling stability thanks to the favourable utilization of the high surface area by the ferrite nanoparticles and the efficient electron transport path through the surface conductive carbon from each active ferrite nanoparticles to a current collector.
Back in the lab, the team plans to explore the design of hybrid nanostructured anodes further by combining these nanoparticles with conductive nanowires or multi-walled carbon nanotubes.
More information can be found in the journal Nanotechnology.
About the author
The work was performed in the Energy & Nano Materials Group at Ajou University, Korea. Prof. Dong-Wan Kim joined the faculty of the Department of Materials Science & Engineering, Ajou University, as assistant professor in 2009. He holds a PhD, a MS and a BS in Materials Science & Engineering (Seoul National University, Korea) and was a senior researcher at Korea Institute of Science & Technology and a postdoc at Massachusetts Institute of Technology, US. He is an author or a co-author of more than 120 scientific papers. Seung-Deok Seo, Hyun-Woo Shim are graduate students in the Energy & Nano Materials Group, which is part of the Department of Materials Science & Engineering at Ajou University. Kyung-Soo Park is a research professor in the group. Yun-Ho Jin (first author) is a researcher from the Plant Engineering Center at the Institute of Advanced Engineering in Korea and used to be an MS student in same group.